"Still a little short of breath tonight but was an incredible show," he Tweeted late Friday. "London fans go hard! 4 SOLD OUT O2 shows in a row!! #BLESSED"

If he wasn't feeling 100 percent, thousands of screaming Beliebers didn't seem to notice as the singer – who turned 19 March 1 – sang, danced and jumped across the stage at London's O2 Arena, which was about 90 percent full.

It's a nice way to end his stay in London, where Bieber also got into a shouting match with a photographer Friday outside his central London hotel and had to be dragged away by his security team.

He made no reference to the incident at Friday's gig or to feeling ill the previous night, when he stopped dancing mid-song and had to take oxygen backstage because of hyperventilation. He ended that night in the care of hospital doctors at the London Clinic.

"Too many blessings to allow the stress in," he Tweeted Friday. "The press made things look nuts but really I have enjoyed London. The fans are incredible."

With his stop in London behind him, Bieber's Believe tour will next head to Lisbon, Portugal.

"So while I have seen some crazy stuff it is all smiles," he Tweeted. "I'm gonna get some rest and keep doing what I love. Entertain all of u. Thanks."